Interesting topic. After years of searching for British rook guns ( double or single ) in original form and more modern or useful Calibres I failed.I did end up with a single and double rook made by holland in 250. Not suitable for my needs. After 10 years of wait Boss have my 5.6 x 50r O/U and PURDEY a 22 Hornet single shot almost ready to deliver. I will use these on rabbit, hare, fox, wallaby, turkey, the odd duck or goose ( head shot of course ) or the neighbours cat. PURDEY have also built a 5.6x52r SxS however in my mind this is outside the ROOK perameter.